Type 1 diabetes (T1D) is a T cell-mediated disease resulting in the destruction of pancreatic beta-cells. CD4 T cells have a prominent role in disease pathogenesis. Moreover, the primary genetic susceptibility determinant has been mapped to the HLA class II DR and DQ loci, encoding for antigen-presenting molecules that are restricting elements for CD4 T cell responses. Genetic polymorphisms controlling the activation and regulation of CD4 T cells are important components of the predisposition to islet autoimmunity. The development of overt diabetes is preceded by a prodromic period during which T cells and immune mediators silently damage beta-cells. Testing for autoantibodies to specific islet cell molecules identifies individuals at high risk of developing T1D. As noted in the RFA to which this application responds to, there is a need for biomarkers that identify people at risk prior to autoantibody appearance. Such biomarkers could allow for earlier and more effective prevention strategies. Micro RNAs (miRNAs) may be a useful biomarker of autoimmunity. The miRNA Registry at the Sanger Institute currently lists 326 miRNA genes. These small RNAs (19-22-mer) influence the post-transcriptional regulation of gene expression by selective binding to complementary messenger RNA sequences and inhibition of translation. Based on computational predictions, up to 20-25% of mammalian genes could be regulated by miRNAs. Emerging literature indicates that unique miRNA expression profiles can be demonstrated in selected cell types and can be associated with human diseases. The objective of this application is to identify miRNAs that may be dysregulated in CD4 T cells in T1D. We will test the hypothesis that selected miRNAs may be over or under expressed in naive CD4 T cells, in the resting state and/or upon activation, and that specific patterns of miRNA expression are associated with T1D; a dysregulation in critical miRNAs may represent an early marker of propensity to autoimmunity, which may precede autoantibodies and help improving prediction. To test this hypothesis, we will assess miRNA expression in peripheral blood CD4 T cells from patients with T1D and their autoantibody-positive and autoantibody-negative relatives using a cross-sectional study design. This feasibility study will establish whether the expression patterns of selected miRNAs in CD4 T cells are associated with T1D, and set the stage for future studies in which miRNAs can be further evaluated as early biomarker of islet autoimmunity in the context of prospective follow-up and clinical trials. [unreadable] [unreadable] [unreadable]